Fix docker and podman examples to work with multiple platforms

[clickthisnick]

Previous behavior is your molecule group would only contain the last platform since the elements were not merging:
https://docs.ansible.com/ansible/latest/collections/ansible/builtin/combine_filter.html

TASK [Display uname info] ******************************************************
ok: [foo] => {
    "msg": "Linux...\n"
}

New behavior is all of your platforms will be in the host inventory

TASK [Display uname info] ******************************************************
ok: [foo] => {
    "msg": "Linux...\n"
}
ok: [bar] => {
    "msg": "Linux...\n"
}

Fixes: #4058